Ultrasonic Flow Meter Transit Time Determination
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Solution Overview
Problem
Existing ultrasonic flow measurement techniques face challenges in accurately determining transit time differences due to computational intensity, parasitic effects, amplitude and phase distortions, and phase noise, which affect measurement accuracy and robustness.
Innovation Solution
The method involves determining a first transit time difference from signal envelopes and a second transit time difference through cross-correlation, using discrete Fourier transforms and window functions to enhance precision and reduce computational effort, with a combination of parallel and serial digital evaluation modules for efficient processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If numerical optimization algorithms are used to determine transit time difference, then measurement accuracy is improved, but computational effort and time increase significantly
Solution Approach 1:
The evaluation is divided into two independent stages: first determining a rough transit time difference from envelope curves, then using this as a starting point for cross-correlation optimization. This segmentation avoids the need for exhaustive numerical optimization while achieving high accuracy.
Solution Approach 2:
The envelope curve analysis is performed as a preliminary step to establish an initial estimate of the transit time difference. This preliminary action provides a good starting point for the subsequent cross-correlation, significantly reducing the computational search space.
2Productivity
If phase offset methods are used to determine transit time difference, then computational effort is reduced, but measurement accuracy deteriorates due to phase noise and temperature dependence
Solution Approach 1:
Envelope curves serve as an intermediary representation of the ultrasonic signals. By analyzing the envelope rather than the raw high-frequency signals directly, the method achieves computational efficiency while avoiding phase noise issues.
Solution Approach 2:
The patent replaces direct phase-based temporal analysis with envelope curve analysis. This substitution eliminates the sensitivity to phase noise and temperature-dependent signal curve variations while maintaining computational efficiency.
3Measurement precision
If signal filtering is applied to determine envelope curves, then transit time difference can be determined, but amplitude and phase distortions are introduced
Solution Approach 1:
The patent uses a simple moving average filter instead of complex filtering methods. This lightweight filtering approach provides sufficient envelope extraction without introducing significant distortions, achieving a good balance between noise reduction and signal fidelity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach achieves high measurement accuracy and robustness with quick arithmetic operations, allowing for precise flow velocity determination and improved measurement resolution beyond the sampling rate.
Implementation Method 1
two ultrasonic transducers (12, 14) are arranged at an angle in the wall of a pipeline (16)... the ultrasonic transducers (12, 14) work alternately as transmitters and receivers
Implementation Method 2
The ultrasonic signals transported by the fluid are accelerated in the direction of flow and decelerated against the direction of flow
Implementation Method 3
determining a first transit time difference from envelopes of the received signals and then, with the knowledge of the first transit time difference... a second transit time difference from a cross-correlation
Data Source
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AI summary
An ultrasonic measuring device (10) for measuring the flow velocity of fluids (18) is described, comprising at least two ultrasonic transducers (12, 14) arranged facing each other, which span a measuring path (24) between them at an angle to the flow through the fluid, and a control and evaluation unit (22) which is designed to alternately transmit an ultrasonic signal on the measuring path (24) with one ultrasonic transducer (12, 14) and to receive it with the other ultrasonic transducer (14, 12) and thus generate a digital first received signal (x) for ultrasound transmitted with the flow (16) and a digital second received signal (y) for ultrasound transmitted against the flow (16) and to determine the flow velocity from a time difference between the first received signal (x) and the second received signal (y).The evaluation unit (22) determines a first transit time difference from a first envelope (xH) of the first received signal (x) and a second envelope (yH) of the second received signal (y), a second transit time difference by evaluating a time window of a cross-correlation (c) of the first received signal (x) and the second received signal (y) determined on the basis of the first transit time difference, and the transit time difference from the first transit time difference and/or the second transit time difference.